Fender bolts will mostly be 5/16 18 thread i believe. Top and bottom of fender at the cab requires a bigger bolt with fine thread. Cowls bolts (4 each side) are same as fender bolts. They tech have a star washer on the head. Review one of the vendor's catalogs and look at pictures.
Can't speak to fuel tank mod, but i would review mar-k site for general info then you can extrapolate.
